Reference is made to U.S. Pat. No. 4,665,614 for its disclosure of electrical contact pins and multiple-contact electric connector assemblies containing such pins and the cooperative engagement and use of such assemblies with thin printed circuit cards of the types for which the present assemblies and electrical contacts are designed. Such assemblies, sometimes referred to as sockets, are designed to receive standard leadless printed circuit cards or modules upon which a number of memory chips are mounted, the chips being connected to electrical contact pads on opposite sides of the card along a contact edge thereof. Such reception involves inserting the contact edge of the card or module within the linear gap formed between pairs of spaced flexible contact legs of a plurality of aligned electrical contact pins supported by an insulation housing. Little or no contact with the pins is made during insertion of the card edge, but the card is then pivoted and locked into place, either vertically or at an angle, during which pivot movement the card engages and flexes the contact legs apart to stress or load the contact leg pairs of the aligned contacts against the spaced contact pads on the circuit card to provide the desired multiple circuit connections.
In conventional sockets or microedge housings, the circuit card is locked into engaged position by opposed small tapered tab members, present on flexible fingers. Insertion of the circuit card forces the side edges of the card over the taper of the opposed tabs and flexing of the fingers until the side edges of the card pass under the small tabs causing the fingers to snap out and engage the side edges of the card and causing the tabs to overlie a small portion of the top surface at each side edge of the card to lock the card in position. Such engagement is restricted to the extreme side edges of the card and is subject to failure if either the side edges of the card or the small tabs are irregular or break. Also such extreme side edge attachment causes greater bowing of the circuit card than is desirable, which bowing is in a direction which can result in slip-release of the engagement.
Microedge connectors are designed with contact housings in pre-determined sizes, shapes and configurations to accommodate different standard printed circuit cards in either vertical or tilted angular alignment. Generally
such cards have circuit pads spaced by 0.05 inch, center to center, with a plurality of pads depending upon the number of circuits present, i.e., 30, 42, 72, etc. Thus, the elongate, insulating contact pin housings have a length and a pin capacity and spacing to accommodate the desired printed circuit cards, i.e., means for mounting the desired number of contact pins in side-by-side alignment, center-spaced by 0.05 inch, the pins being up to about 0.035 inch in thickness or width in order to provide adequate spacing therebetween under conditions of use.
Since flexible connector pins of the types used in multi-contact, microedge connectors are small, delicate and subjected to flexing during each insertion and removal of a printed circuit card, such pins are susceptible to distortion and/or breakage if the flexible contact legs thereof are bent or deflected in the wrong direction during linear insertion of the card edge, or if the legs are flexed open to an excessive extent during pivot-attachment of the card. These problems are reduced by providing an adequate insertion gap or space between the contact legs to permit insertion of the card edge with little or no contact with either of the legs, i.e., no insertion force required. However, the design of the connector pins must be such that the contact legs engage the circuit card contact zones with sufficient force when the card is pivoted or snapped into final position to provide satisfactory electrical conduction under the conditions of use.
Also, in cases where overstress or over-flexing of the contact pins is prevented by a portion of the pin engaging another portion of the pin, i.e., a shoulder portion or adjacent areas of the opening of a flexible loop portion, the structure of the pins and the housing is difficult to produce and to assemble, and/or the restraining force is dependent upon straight engagement between portions of the thin pins which generally have a thickness of between 0.005 and 0.025 inch. Such metal-to-metal contact can result in over-ride slippage, jamming, wear and/or warping and failure of the intended overstress prevention results.